Process of producing soluble tanning agents.



' soluble, in cold water.

ERIOH DEHNEL, OF LUDWIGSHAFEN-ON-THE-RHINE, GERMANY, 'ASSIGNOR TO BADISCHE ANILIN & SODA FABRIK, OF LUDWIG-SHAFI IN-ON-THE RHINE, GER

MANY, A CORPORATION OF BADEN.

PROCESS OF PRODUCING SOLUBLE TANNING AGENTS No Drawing.

To all whom it may concern:

Be it known that I, Enron DEHNEL, citizen of the German Empire, residing at Ludwigshafen-on-the-Rhine, Germany, have invented a new and useful Process of Producing Soluble Tanning Agents, of which the following is a specification.

Several of the natural tanning agents, whether inthe form of extract, or not, have the undesirable property of being either only diificultly soluble, or insufliciently Thus for instance the ingredients of the valuble quebracho extract which possess tanning properties are, in a large proportion, insoluble, or diflicultly soluble. I have found that such natural tanning extracts can be converted into products which are readily soluble in cold water by treating them with soluble condensation products of aromatic phenols, which products possess at least one hydroxyl group and at least one salt forming group, such for instance as the sulfonic acid group. Such condensation products can be formed either in the presence or absence of formaldehyde, the' formaldehyde when used apparently taking part in the formation of the condensation product. When the condensation is carried out in the presence of formaldehyde, the reaction can beeffected either by treatinga phenolic body with formaldehyde in the presence of dilute acid and then sul fonating the insoluble condensation products bytreatment with strong sulfuric acid until they are soluble in water, or the reaction product of a phenolic body with concentrated sulfuric acid, or a phenol sulfo acid, or a mixture of a phenol and a phenol sulfoacid, can be treated with formaldehyde. The action of the formaldehyde on the sulfonation products of the phenolic body is preferably effected under mild conditions, that it to say, while avoiding too high a temperature, or too great an excess of for maldehyde as otherwise the well-known products, insoluble in water, may result. When the condensation products are produced in the absence of formaldehyde, itis preferred to carry out the reaction by heating a phenol sulfonic acid under diminshed pressure and, if desired, a condensation agent (such, for instance, as phosphorous trichlorid, phosphorous oxy-chlorid, or

Specification of Letters Patent.

Patented Mar. 23, 1915.

Application filed June 30, 1913. Serial No. 776,545.

The process of my invention gives rise to products which are soluble in cold water and are therefore eminently adapted for use in tanning. The, said process can be carried out eltherby adding the said condensation product to the-prepared tanning extract, or

to the difficultly soluble parts thereof. Or

it is equivalent to add the said product to the thin solution which. is at first obtained and then subsequently to concentrate the treated solution. The mixtures can be effected, or maintained, either-at ordinary temperatures, or at raised temperatures. In some cases, the addition'of the condensation product to the tanning extract'tends to bleach the said extract, and this is a further advantage.

' The following example will serve to illustrate further the nature of my invention and the manner of performing the same, but the invention is not limited to this example. The parts are by weight. Treat 500 parts of quebracho extract (such as can be obtained directly by simple extraction of quebracho Wood, with water, and possesses a specific gravity of about from 18 to 20 B. at a temperature of 40 C.) with 200 parts of the sodium salt of the product obtained from formaldehyde and cresol-sulfonic acid,

. tanning extracts, such for instance as mangrove and chestnut, can be treated with similar results. i a

Now what I claim is 1. The process of converting diificultly soluble or insufliciently soluble tanningem tracts into more soluble compounds b treating such diflicultly soluble or insu ciently soluble extracts with a soluble condensation product of an aromatic phenol, which condensation product possesses at least one 'as described in Example 1 of the specifica- I tion of British Patent No. 8511 A. D. 1912,

hydroxyl group and also at least one saltgroup and issoluble in water, yielding an forming group. almost colorless solution which becomes 2. The process of converting dillicultly deeply colored on the addition of a solution soluble or insufliciently soluble tanning exof a ferric salt. 15

5 tracts into more soluble compounds by treat- In. testimony whereof l have hereunto set ing such diflicultly soluble or insufficiently my hand in the presence of two subscribing .soluble extracts with a condensation prod-, witnesses.

uct obtainable by acting on cresol with sul- ERICH D EHNEL, furic acid and formaldehyde, which conden- Witnesses: 10 sation product possesses at least one hy- J. ALEG. LLOYD,

droxyl group and at least one sulfonic acid JOSEPH: PFEIFFER. 

